//  Copyright (c) 2020 ETH Zurich
//  Copyright (c) 2015 Daniel Bourgeois
//  Copyright (c) 2017-2023 Hartmut Kaiser
//
//  SPDX-License-Identifier: BSL-1.0
//  Distributed under the Boost Software License, Version 1.0. (See accompanying
//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

/// \page hpx::ranges::is_partitioned
/// \headerfile hpx/algorithm.hpp

#pragma once

#if defined(DOXYGEN)
namespace hpx { namespace ranges {
    // clang-format off

    /// Determines if the range [first, last) is partitioned.
    ///
    /// \note   Complexity: at most (N) predicate evaluations where
    ///         \a N = distance(first, last).
    ///
    /// \tparam FwdIter     The type of the source iterators used for the
    ///                     This iterator type must meet the requirements of a
    ///                     forward iterator.
    /// \tparam Sent        The type of the source sentinel (deduced). This
    ///                     sentinel type must be a sentinel for FwdIter.
    /// \tparam Pred        The type of the function/function object to use
    ///                     (deduced).
    /// \tparam Proj        The type of an optional projection function. This
    ///                     defaults to \a hpx::identity.
    /// \param first        Refers to the beginning of the sequence of elements
    ///                     of that the algorithm will be applied to.
    /// \param last         Refers to the end of the sequence of elements of
    ///                     that the algorithm will be applied to.
    /// \param pred         Refers to the unary predicate which returns true
    ///                     for elements expected to be found in the beginning
    ///                     of the range. The signature of the function
    ///                     should be equivalent to
    ///                     \code
    ///                     bool pred(const Type &a);
    ///                     \endcode \n
    ///                     The signature does not need to have const &, but
    ///                     the function must not modify the objects passed to
    ///                     it. The type \a Type must be such that objects of
    ///                     types \a FwdIter can be dereferenced and then
    ///                     implicitly converted to Type.
    /// \param proj         Specifies the function (or function object) which
    ///                     will be invoked for each of the elements as a
    ///                     projection operation before the actual predicate
    ///                     \a is invoked.
    ///
    /// \returns  The \a is_partitioned algorithm returns \a bool.
    ///           The \a is_partitioned algorithm returns true if each element
    ///           in the sequence for which pred returns true precedes those for
    ///           which pred returns false. Otherwise is_partitioned returns
    ///           false. If the range [first, last) contains less than two
    ///           elements, the function is always true.
    ///
    template <typename FwdIter, typename Sent,
        typename Pred,
        typename Proj = hpx::identity>
    bool is_partitioned(
        FwdIter first, Sent last, Pred&& pred, Proj&& proj = Proj());

    /// Determines if the range [first, last) is partitioned.
    ///
    /// \note   Complexity: at most (N) predicate evaluations where
    ///         \a N = distance(first, last).
    ///
    /// \tparam ExPolicy    The type of the execution policy to use (deduced).
    ///                     It describes the manner in which the execution
    ///                     of the algorithm may be parallelized and the manner
    ///                     in which it executes the assignments.
    /// \tparam FwdIter     The type of the source iterators used for the
    ///                     This iterator type must meet the requirements of a
    ///                     forward iterator.
    /// \tparam Sent        The type of the source sentinel (deduced). This
    ///                     sentinel type must be a sentinel for FwdIter.
    /// \tparam Pred        The type of the function/function object to use
    ///                     (deduced). \a Pred must be \a CopyConstructible
    ///                     when using a parallel policy.
    /// \tparam Proj        The type of an optional projection function. This
    ///                     defaults to \a hpx::identity.
    /// \param policy       The execution policy to use for the scheduling of
    ///                     the iterations.
    /// \param first        Refers to the beginning of the sequence of elements
    ///                     of that the algorithm will be applied to.
    /// \param last         Refers to the end of the sequence of elements of
    ///                     that the algorithm will be applied to.
    /// \param pred         Refers to the unary predicate which returns true
    ///                     for elements expected to be found in the beginning
    ///                     of the range. The signature of the function
    ///                     should be equivalent to
    ///                     \code
    ///                     bool pred(const Type &a);
    ///                     \endcode \n
    ///                     The signature does not need to have const &, but
    ///                     the function must not modify the objects passed to
    ///                     it. The type \a Type must be such that objects of
    ///                     types \a FwdIter can be dereferenced and then
    ///                     implicitly converted to Type.
    /// \param proj         Specifies the function (or function object) which
    ///                     will be invoked for each of the elements as a
    ///                     projection operation before the actual predicate
    ///                     \a is invoked.
    ///
    /// The predicate operations in the parallel \a is_partitioned algorithm invoked
    /// with an execution policy object of type \a sequenced_policy
    /// executes in sequential order in the calling thread.
    ///
    /// The comparison operations in the parallel \a is_partitioned algorithm invoked
    /// with an execution policy object of type \a parallel_policy
    /// or \a parallel_task_policy are permitted to execute in an unordered
    /// fashion in unspecified threads, and indeterminately sequenced
    /// within each thread.
    ///
    /// \returns  The \a is_partitioned algorithm returns a \a hpx::future<bool>
    ///           if the execution policy is of type \a task_execution_policy
    ///           and returns \a bool otherwise.
    ///           The \a is_partitioned algorithm returns true if each element
    ///           in the sequence for which pred returns true precedes those for
    ///           which pred returns false. Otherwise is_partitioned returns
    ///           false. If the range [first, last) contains less than two
    ///           elements, the function is always true.
    ///
    template <typename ExPolicy, typename FwdIter, typename Sent,
        typename Pred,
        typename Proj = hpx::identity>
    hpx::parallel::util::detail::algorithm_result_t<ExPolicy, bool>
    is_partitioned(ExPolicy&& policy, FwdIter first, Sent last, Pred&& pred,
        Proj&& proj = Proj());

    /// Determines if the range rng is partitioned.
    ///
    /// \note   Complexity: at most (N) predicate evaluations where
    ///         \a N = std::size(rng).
    ///
    /// \tparam Rng         The type of the source range used (deduced).
    ///                     The iterators extracted from this range type must
    ///                     meet the requirements of an forward iterator.
    /// \tparam Pred        The type of the function/function object to use
    ///                     (deduced).
    /// \tparam Proj        The type of an optional projection function. This
    ///                     defaults to \a hpx::identity.
    /// \param rng          Refers to the sequence of elements the algorithm
    ///                     will be applied to.
    /// \param pred         Refers to the unary predicate which returns true
    ///                     for elements expected to be found in the beginning
    ///                     of the range. The signature of the function
    ///                     should be equivalent to
    ///                     \code
    ///                     bool pred(const Type &a);
    ///                     \endcode \n
    ///                     The signature does not need to have const &, but
    ///                     the function must not modify the objects passed to
    ///                     it. The type \a Type must be such that objects of
    ///                     types \a FwdIter can be dereferenced and then
    ///                     implicitly converted to Type.
    /// \param proj         Specifies the function (or function object) which
    ///                     will be invoked for each of the elements as a
    ///                     projection operation before the actual predicate
    ///                     \a is invoked.
    ///
    /// \returns  The \a is_partitioned algorithm returns \a bool.
    ///           The \a is_partitioned algorithm returns true if each element
    ///           in the sequence for which pred returns true precedes those for
    ///           which pred returns false. Otherwise is_partitioned returns
    ///           false. If the range rng contains less than two
    ///           elements, the function is always true.
    ///
    template <typename Rng,
        typename Pred,
        typename Proj = hpx::identity>
    bool is_partitioned(Rng&& rng, Pred&& pred, Proj&& proj = Proj());

    /// Determines if the range [first, last) is partitioned.
    ///
    /// \note   Complexity: at most (N) predicate evaluations where
    ///         \a N = std::size(rng).
    ///
    /// \tparam ExPolicy    The type of the execution policy to use (deduced).
    ///                     It describes the manner in which the execution
    ///                     of the algorithm may be parallelized and the manner
    ///                     in which it executes the assignments.
    /// \tparam Rng         The type of the source range used (deduced).
    ///                     The iterators extracted from this range type must
    ///                     meet the requirements of an forward iterator.
    /// \tparam Pred        The type of the function/function object to use
    ///                     (deduced). \a Pred must be \a CopyConstructible
    ///                     when using a parallel policy.
    /// \tparam Proj        The type of an optional projection function. This
    ///                     defaults to \a hpx::identity.
    /// \param policy       The execution policy to use for the scheduling of
    ///                     the iterations.
    /// \param rng          Refers to the sequence of elements the algorithm
    ///                     will be applied to.
    /// \param pred         Refers to the unary predicate which returns true
    ///                     for elements expected to be found in the beginning
    ///                     of the range. The signature of the function
    ///                     should be equivalent to
    ///                     \code
    ///                     bool pred(const Type &a);
    ///                     \endcode \n
    ///                     The signature does not need to have const &, but
    ///                     the function must not modify the objects passed to
    ///                     it. The type \a Type must be such that objects of
    ///                     types \a FwdIter can be dereferenced and then
    ///                     implicitly converted to Type.
    /// \param proj         Specifies the function (or function object) which
    ///                     will be invoked for each of the elements as a
    ///                     projection operation before the actual predicate
    ///                     \a is invoked.
    ///
    /// The predicate operations in the parallel \a is_partitioned algorithm invoked
    /// with an execution policy object of type \a sequenced_policy
    /// executes in sequential order in the calling thread.
    ///
    /// The comparison operations in the parallel \a is_partitioned algorithm invoked
    /// with an execution policy object of type \a parallel_policy
    /// or \a parallel_task_policy are permitted to execute in an unordered
    /// fashion in unspecified threads, and indeterminately sequenced
    /// within each thread.
    ///
    /// \returns  The \a is_partitioned algorithm returns a \a hpx::future<bool>
    ///           if the execution policy is of type \a task_execution_policy
    ///           and returns \a bool otherwise.
    ///           The \a is_partitioned algorithm returns true if each element
    ///           in the sequence for which pred returns true precedes those for
    ///           which pred returns false. Otherwise is_partitioned returns
    ///           false. If the range rng contains less than two
    ///           elements, the function is always true.
    ///
    template <typename ExPolicy, typename Rng,
        typename Pred,
        typename Proj = hpx::identity>
    hpx::parallel::util::detail::algorithm_result_t<ExPolicy, bool>
    is_partitioned(
        ExPolicy&& policy, Rng&& rng, Pred&& pred, Proj&& proj = Proj());
    // clang-format on
}}    // namespace hpx::ranges
#else

#include <hpx/config.hpp>
#include <hpx/algorithms/traits/projected.hpp>
#include <hpx/algorithms/traits/projected_range.hpp>
#include <hpx/modules/executors.hpp>
#include <hpx/parallel/algorithms/is_partitioned.hpp>
#include <hpx/parallel/util/detail/algorithm_result.hpp>
#include <hpx/parallel/util/detail/sender_util.hpp>

#include <algorithm>
#include <cstddef>
#include <iterator>
#include <type_traits>
#include <utility>

namespace hpx::ranges {

    HPX_CXX_EXPORT inline constexpr struct is_partitioned_t final
      : hpx::detail::tag_parallel_algorithm<is_partitioned_t>
    {
    private:
        template <typename FwdIter, typename Sent, typename Pred,
            typename Proj = hpx::identity>
        // clang-format off
            requires(
                hpx::traits::is_forward_iterator_v<FwdIter> &&
                hpx::traits::is_sentinel_for_v<Sent, FwdIter> &&
                hpx::parallel::traits::is_projected_v<Proj, FwdIter> &&
                hpx::parallel::traits::is_indirect_callable_v<
                    hpx::execution::sequenced_policy, Pred,
                    hpx::parallel::traits::projected<Proj, FwdIter>
                >
            )
        // clang-format on
        friend bool tag_fallback_invoke(hpx::ranges::is_partitioned_t,
            FwdIter first, Sent last, Pred pred, Proj proj = Proj())
        {
            return hpx::parallel::detail::is_partitioned<FwdIter, Sent>().call(
                hpx::execution::seq, first, last, HPX_MOVE(pred),
                HPX_MOVE(proj));
        }

        template <typename ExPolicy, typename FwdIter, typename Sent,
            typename Pred, typename Proj = hpx::identity>
        // clang-format off
            requires(
                hpx::is_execution_policy_v<ExPolicy> &&
                hpx::traits::is_forward_iterator_v<FwdIter> &&
                hpx::parallel::traits::is_projected_v<Proj, FwdIter> &&
                hpx::parallel::traits::is_indirect_callable_v<
                    hpx::execution::sequenced_policy, Pred,
                    hpx::parallel::traits::projected<Proj, FwdIter>
                >
            )
        // clang-format on
        friend typename parallel::util::detail::algorithm_result<ExPolicy,
            bool>::type
        tag_fallback_invoke(hpx::ranges::is_partitioned_t, ExPolicy&& policy,
            FwdIter first, Sent last, Pred pred, Proj proj = Proj())
        {
            return hpx::parallel::detail::is_partitioned<FwdIter, Sent>().call(
                HPX_FORWARD(ExPolicy, policy), first, last, HPX_MOVE(pred),
                HPX_MOVE(proj));
        }

        template <typename Rng, typename Pred, typename Proj = hpx::identity>
        // clang-format off
            requires(
                hpx::traits::is_range_v<Rng> &&
                hpx::parallel::traits::is_projected_range_v<Proj, Rng> &&
                hpx::parallel::traits::is_indirect_callable_v<
                    hpx::execution::sequenced_policy, Pred,
                    hpx::parallel::traits::projected_range<Proj, Rng>
                >
            )
        // clang-format on
        friend bool tag_fallback_invoke(hpx::ranges::is_partitioned_t,
            Rng&& rng, Pred& pred, Proj proj = Proj())
        {
            using iterator_type =
                typename hpx::traits::range_traits<Rng>::iterator_type;

            return hpx::parallel::detail::is_partitioned<iterator_type,
                iterator_type>()
                .call(hpx::execution::seq, std::begin(rng), std::end(rng),
                    HPX_MOVE(pred), HPX_MOVE(proj));
        }

        template <typename ExPolicy, typename Rng, typename Pred,
            typename Proj = hpx::identity>
        // clang-format off
            requires(
                hpx::is_execution_policy_v<ExPolicy> &&
                hpx::traits::is_range_v<Rng> &&
                hpx::parallel::traits::is_projected_range_v<Proj, Rng> &&
                hpx::parallel::traits::is_indirect_callable_v<
                    hpx::execution::sequenced_policy, Pred,
                    hpx::parallel::traits::projected_range<Proj, Rng>
                >
            )
        // clang-format on
        friend parallel::util::detail::algorithm_result_t<ExPolicy, bool>
        tag_fallback_invoke(hpx::ranges::is_partitioned_t, ExPolicy&& policy,
            Rng&& rng, Pred pred, Proj proj = Proj())
        {
            using iterator_type =
                typename hpx::traits::range_traits<Rng>::iterator_type;

            return hpx::parallel::detail::is_partitioned<iterator_type,
                iterator_type>()
                .call(HPX_FORWARD(ExPolicy, policy), std::begin(rng),
                    std::end(rng), HPX_MOVE(pred), HPX_MOVE(proj));
        }
    } is_partitioned{};
}    // namespace hpx::ranges

#endif
